R merge_element() error with no apparent reason (ggplot2)-CodePudding

So here is a very short example for the code:

mtcars %>% ggplot(aes(x=wt,y=mpg,group=1)) 
  geom_point() geom_line() 
  theme(panel.grid = element_rect(fill = "grey"),
        axis.text = element_text(face = "bold"))

Error in `**merge_element()**`:
! Only elements of the same class can be merged
Run `rlang::last_error()` to see where the error occurred.

This is such an annoying error, and I also tried other solutions in the forum but it really seems like something R folks should take care of. This error is prevented by adding a simple theme_bw() (or alike) argument, but it then cancels the text argument within theme()

mtcars %>% ggplot(aes(x=wt,y=mpg,group=1)) 
  geom_point() geom_line() 
  theme(panel.grid = element_rect(fill = "grey"),
        axis.text = element_text(face = "bold")) 
  theme_minimal()

This works but doesnt apply the axis.text.

Any suggestions?

I excepted to get a figure with bolded text on the axes, and it never happend

CodePudding user response：

The issue here is that the panel.grid is composed of lines and so the theme element to modify is element_line().

If you want to change the fill, you should be using panel.background.

mtcars %>% 
    ggplot(aes(x = wt, y = mpg))  
    geom_point()  
    geom_line()  
    theme(axis.text = element_text(face = "bold"), 
          panel.background  = element_rect(fill = "grey"))

Result:

On the other hand if you're trying to change the grid line colour then you should be using element_line(color = ...):

mtcars %>% 
  ggplot(aes(x = wt, y = mpg))  
  geom_point()  
  geom_line()  
  theme(axis.text = element_text(face = "bold"), 
        panel.grid  = element_line(color = "grey"))

Result: